Use Cases, User Stories and Requirements

Use Case Specification

The slide shows the use case specification from this year’s coursework. It
highlights the attributes of use case specifications that can be mapped onto
user stories – these are the use case precis and, perhaps, functional
requirements at the use case level. What is more interesting is what use
stories do not include in the specification. These include non-functional
requirements – there is no systematic means of documenting quality
requirements in user stories. One problem is that many quality requirements
are expressed at a system level, i.e. the desired quality of the system. In
contrast user stories are designed to identify functions and behaviours that
can be implemented in a single sprint. It begs the question where important
quality requirements can be specified.
User stories are designed not to include specifications of behaviour. This
required behaviour is intended to emerge from communication between users
and developers. Likewise there are no attributes of the specified system
documented. The other important requirements element that is not
documented directly in user stories is the measurable fit criteria. But this is not
to say that such requirements tests are not included in agile development
methods. More on these in the following slides.
One of the biggest misunderstandings with user stories is how they differ from
traditional requirements specifications. The biggest difference is in the level of
detail. User stories should only provide enough detail to make a reasonably
low risk estimate of how long the story will take to implement. When the time
comes to implement the story developers will go to the customer and receive
a detailed description of the requirements face to face

Reference: Neil Maiden (2011) Requirements Engineering Lecture Notes

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